The long term goals of this project are to examine the factors that led to the recent emergence of Hendra virus (HeV) and Nipah virus (NiV) in Australia and southeast Asia. Substantial data implicate fruit bats as reservoir hosts for these viruses. Both moved into human populations via domestic animal "amplifier" hosts (horses for HeV and pigs for NiV) and caused fatal disease in humans; NiV in particular was responsible for the death of over 100 people in 1999. Little is known of the underlying causes of emergence, but three plausible factors have been proposed: encroachment of humans/domestic animals into fruit bat habitat; climate change; and alterations to fruit bat migration patterns. Our aim is to investigate the role of these anthropogenic factors in emergence, and to set up a series of key experiments to understand the mode of transmission between host species more clearly. These viruses are part of a growing group of novel zoonotic paramyxoviruses harbored by fruit bats. Their recent emergence, high case fatality rate in humans and the potentially large pool of other, related viruses in fruit bats suggests that these are a significant threat to human health beyond their current distribution. Understanding their emergence will have a significant impact on future surveillance and control programs. In particular, a component of this project is to develop a predictive, parameterized (via experimental and field data) mathematical model for NiV and HeV emergence.